Companion object that facilitates the importing of ValueEither members as
an alternative to mixing it in. One use case is to import EitherValues's members so you can use
left.value and right.value on Either in the Scala interpreter:

scala> e.right.value should be < 9
org.scalatest.TestFailedException: The Either on which rightValue was invoked was not defined.
at org.scalatest.EitherValues$RightValuable.value(EitherValues.scala:148)
at .<init>(<console>:18)
...